The gas in an internal combustion engine contains gas state components, PM (Particulate Matter, can say Particulate), unburned hydrocarbons (UBS or HC), carbon monoxide (CO), nitric oxides (NOX), carbon dioxide (CO2), water vapor (H2O), oxygen (O2), and nitrogen (N2) and so on. PM in exhaust gas from, for example diesel among internal combustion engines, points solid or liquid particles larger than 10 μm. The solid or liquid particles include soot consisting of carbonaceous, combustible organic fraction that consists high-boiling-point carbon hydride and sulfate moieties.
For example, Patent Document 1 discloses a discharge type exhaust gas control apparatus that includes a diesel particulate filter and a plasma generator as an exhaust gas control apparatus for eliminating these components from exhaust gas. The diesel particulate filter is installed in the exhaust passage. The plasma generator is combined with the diesel particulate filter or installed upstream of the filter. The plasma generator stably supplies NO2 and active substances (active oxygen), which are needed for the combustion (oxidation) of exhaust particulates collected by the particulate filter, in the discharge-type exhaust gas control apparatus.
Patent Document 2 discloses an exhaust gas control apparatus comprising an after-treatment device which cleans aeration exhaust gas in the middle of exhaust pipe from an internal combustion engine. The exhaust gas control apparatus includes a plasma generator, flow-through oxidation catalyst, a means of adding fuel and increasing the temperature. The plasma generator generates plasma by discharging into the exhaust gas above the after-treatment device. The style oxidation catalyst is installed before the plasma generator. Fuel is added to the exhaust gas before the oxidation catalyst by the means of adding fuel. The means of increasing the temperature elevates temperature of exhaust gas until occurring oxidation, on the oxidation catalyst, of fuel added by the means of adding fuel. Using this apparatus to energize exhaust gas with the discharge of the plasma generator into the exhaust gas, the unburned carbon hydride is converted into active radicals, oxygen into ozone, NO into NO2. These exhaust gas components becomes active, resulting in a greater exhaust purification effect than with existing after-treatment devices from low temperature area.
Patent Document 3 discloses an after-treatment method for exhaust gas and apparatus for it. In this apparatus, an after-treatment unit for exhaust gas, a particulate filter, is placed in the exhaust pipe and an oxidation reactor, a plasma reactor, is installed upstream from it. When the oxidation reactor generates non-heat plasma in the exhaust gas flowing through the oxidation reactor, oxidants are generated from the exhaust gas components. As the result, soot is incinerated with the oxidants in the particulate filter, and reproduced.
Patent Document 4 discloses an exhaust gas purification apparatus. It contains a filter that catches particulate matter, an absorbent that absorb components of the exhaust gas, and a plasma generator that generate plasma with applied voltage, in exhaust smoke path of the internal combustion engine. The exhaust gas purification apparatus eliminates the accumulated particles on the filter and absorbent material or the exhaust gas components at normal temperature below the particulate ignition temperature. It enables the removal of harmful substances and particulates contained in internal combustion engine gases, such as diesel exhaust gas, at exhaust temperatures below 150° C.
Patent Document 5 discloses an exhaust purification apparatus comprising a means of purification and a means of forming plasma. The purifier is installed in the exhaust path of the internal combustion engine, and contains NOx-absorbing materials and/or a particle filter. The means of forming plasma is installed in the exhaust path. The exhaust purification apparatus comprises a means of detecting oxygen density and controlling means. The means of detecting oxygen density detects oxygen density in exhaust gas. The controlling means results in the purification of the exhaust gas due to the means of purification when the oxygen density on the means of detecting oxygen density, decreasing the oxygen density in the exhaust gas while simultaneously driving the means of forming plasma when the amount of absorbed material exceeds a predetermined value. If applying this apparatus for stationary fuel system, such as steam generator and gas turbine, or transferring fuel system such as diesel automobile, the cost is lower than that of existing plasma processes because of un-necessity of firm power. Moreover it will be possible to remove NOx and soot at the same time effectively by plasma desorption at high density.
Patent Document 6 discloses a ways to reduce particle matter included in the exhaust gas from a lean-burn engine. In the ways to reduce particle matter, plasma is generated in the exhaust gas, includes particle matter, from lean-burn engine etc. As the result, several carbon dioxide and ozone are generated and the particle matter is oxidized by these carbon dioxide and ozone.
Patent Document 7 discloses an exhaust gas breaking apparatus. This exhaust gas breaking apparatus comprises a microwave oscillation device, microwave resonant cavity, microwave radiation means, and ignition means using plasma. The microwave oscillation device generates certain microwave marginal zone. The microwave resonant cavity resonates part of the microwave zone. The microwave radiation means radiates microwave to the microwave resonant cavity. The ignition means forms gas plasma by partly discharging in the gas inside said microwave resonant cavity. Said microwave radiation mean is arranged in circumferential direction in periphery of flow path where exhaust gas flows. Said microwave radiation mean is a microwave radiating antenna with a configuration and size such that a strong electric field place, where plasma generating area generated with microwave becomes the same in the passage section, is generated. Applying this apparatus, carbon-carbon and carbon-hydrogen bonds are broken by the strong oxidation power of ozone and OH radicals along with plasma generation in exhaust gas, including unborn gas, soot, and NOx in combustion/reactive room. As a result, it becomes stabilizes harmless oxide such as NO2 and CO2 or carbon via the chemical reaction involving oxidation and OH radicals. The exhaust gas components are rendered harmless.
[Patent Document 1] Japanese Patent Application Laid-open Publication No. 2002-276333
[Patent Document 2] Japanese Patent Application Laid-open Publication No. 2004-353596
[Patent Document 3] Japanese Patent Application Laid-open Publication No. 2005-502823
[Patent Document 4] Japanese Patent Application Laid-open Publication No. 2004-293522
[Patent Document 5] Japanese Patent Application Laid-open Publication No. 2006-132483
[Patent Document 6] Japanese Patent Application Laid-open Publication No. 2004-169643
[Patent Document 7] Japanese Patent Application Laid-open Publication No. 2007-113570